1. Technical Field
This invention relates to thrust bearing arrangements for supporting working surfaces, such as thrust faces of rotary shafts and the like, wherein the bearing is provided by an annular array of discrete bearing pad surfaces, and in particular relates to such thrust bearings of the tilting pad type wherein each such bearing pad surface is able to tilt with respect to the direction of relative rotation to permit the formation of a wedge-shaped hydrodynamic film of lubricant thereat.
2. Related Art
It is known to form such bearing arrangements from discrete bearing pads assembled individually with respect to a carrier and permitted to tilt by way of individual and shared elements whose assembly contributes significantly to the cost of the arrangement. It is also known to have such a thrust bearing arranged wherein the individual bearing surfaces are defined on an integral ring, as notionally separate pads joined to each other by an integral and somewhat flexible web. However, such a configuration is unduly stiff in respect of tilting unless the web is formed by expensive precision machinery, although because the web comprises the material forming the bulk of the pads and chosen for its load bearing rather than flexing properties, such construction is inherently stiff.
Examples of tilting pad thrust bearings are known from GB-A-2308162 and GB-A-1535165 which illustrate various degrees of construction complexity depending upon the property to be used to advantage.
It is an object of the present invention to provide a tilting pad thrust bearing of simple design and capable of simple and cost effective manufacture.
According to a first aspect of the present invention a tilting pad thrust bearing arrangement comprises (a) a rigid backing surface surrounding a longitudinal axis and facing a first direction along the longitudinal axis, (b) a plurality of bearing pads disposed overlying said backing surface arrayed about the longitudinal axis and each having on opposite faces thereof a substantially flat bearing surface facing along the longitudinal axis in said first direction and a substantially flat supported surface facing axially towards the backing surface, and (c) intermediate the backing surface and pads, mounting means comprising (i) support surface means, defined coaxially with respect to the backing surface, (ii) a circumferentially continuous or discontinuous annular mounting ring of incompressible resilient material coaxial with respect to the backing surface providing, having associated with each pad, a circumferentially extending sector defined between mounting points at each side of the pad spaced from the support surface thereat by a predetermined stand-off distance, (iii) and characterised by headed fastening means extending through the ring sector associated with each pad and clamping the supported surface of the pad with respect to said ring sector defining a clamped region thereof, the headed fastening means comprising at least one headed fastener having a head dimensioned to extend axially from the clamped region of the ring sector into abutment with the support surface means to bias the clamped region away from the support surface means and shaped to form, by said abutment, a pivot for the bearing pad and associated ring sector.
The headed fastening means may comprise a single fastener having a shank portion and a head portion. The fastener may be made of harder material than the support surface means.
According to a second aspect of the present invention a method of manufacturing the tilting pad thrust bearing arrangement according to the preceding paragraph comprises disposing the bearing pads in a circular array, securing the mounting ring sectors to their associated pads, disposing the bearing pads and clamping ring sector adjacent the backing surface, applying an axial clamping force between the bearing pads and backing. surface to bed each fastener head with respect to the support surface and define a substantially uniform distance between the bearing surfaces and the backing surface.